1. Technical Field
The present invention relates to a circuit board and a display device including the same and, in particular, to a circuit board including differential signal lines and a display device including the same.
2. Description of Related Art
Flat panel displays, such as a liquid crystal display (LCD), a plasma display device (PDP), a field emission display (FED), a vacuum fluorescent display (VFD), and an organic light emitting display (OLED) are widely used.
These display devices generally include a display panel and a signal controller for supplying signals to the display panel. The display panel receives the signals through a flexible printed circuit film connected to the signal controller. The signal controller includes a TCON (timing controller) and an IC chip (integrated circuit chip), and they are connected to wirings that are arranged at the same layer or at a different layer. The flexible printed circuit film includes a film, a plurality of wirings arranged parallel to each other on the film, and a passivation layer formed on the wirings.
The essential semiconductors, such as the TCON and the IC chip, have become complicated due to an increase in size and display quality of the display devices. Accordingly, resolution of various technical problems is required, and particularly, an improvement of a data transmission method is strongly required to prevent the deterioration of the display quality due to noise and signal delay.
For example, the signal transmission speed is low, the consumption of current is large, and EMI (electromagnetic interference) characteristic are poor in the case of a TTL (transistor-to-transistor logic) as a data transmission method between an LDI (LCD driver IC) and the conventional TCON. There are LVDS (low voltage differential signaling) and RSDS (reduced signal differential signaling) as methods to compensate this, and the EMI characteristic is improved by reducing the swing size of the signal in the conventional TTL method and the transmission speed of the signal is improved. Also, a smaller amount of wiring than in the conventional TTL method may be used. Recently, interface techniques, such as mini-LVDS and PPDS (point-to-point differential signaling), have been researched.
However, while the EMI characteristic may be improved in the low frequency band with the LVDS or RSDS methods, the EMI characteristic is not improved at a high frequency. If the high frequency region of 800 MHz to 6 GHz is used, in the case of a wireless wide area network and a wireless local area network, the EMI characteristic is not improved in this frequency region even if though the LVDS or the RSDS are used. To improve the display quality of the display device, the EMI should be reduced.